Model Tess Holliday says 'the hate has been overwhelming' after announcing she has anorexia. Why?

Plus-sized model Tess Holliday's anorexia nervosa diagnosis has kindled disbelief and fat phobia that experts say contributes to a grave misunderstanding of disordered eating.

"I’m anorexic & in recovery. I’m not ashamed to say it out loud anymore," Holliday tweeted on May 1. "I’m the result of a culture that celebrates thinness & equates that to worth, but I get to write my own narrative now. I’m finally able to care for a body that I’ve punished my entire life & I am finally free."

Many of Holliday's 92k Twitter followers thanked her for opening up. "It's so important that people know that anyone of any shape or size can have anorexia," one tweeted. Another wrote, "The narrative around [eating disorders] needs to be widened to include people of all sizes."

But many would not accept the idea. "Anorexic???? I think you mean body dysmorphia..." tweeted a user. "Someone that weight is not anorexic," one added. "It's actually insulting to people who are starving themselves to death." And: "She's the opposite of anorexic."

On Thursday, Holliday, 35, told Good Morning America that even she had struggled to accept the diagnosis. "I always thought that I overate,” she said. “But then, people in my life would say, ‘Oh yeah, I ate more than Tess’ and it was almost like I wore it as a badge of honor.”

“I’ve had a lot of messages from folks that are anorexic that are livid and angry because they feel like I’m lying,” she added. “I am plus size, but advocating for diversity and larger bodies, and so I think for people hearing me say I’m anorexic was really jarring and hard and confusing.” Holliday's body-positive activism is seen in both her modeling work and her #EffYourBeautyStandards initiative, which celebrates diversity in social media photos.

On Thursday, Holliday addressed the public reaction to her news. "The last few days have been some of my toughest to date since becoming a public figure," she wrote on Instagram. "The hate has been overwhelming, but the messages from those of you that felt seen, validated, & loved far outweigh the critics."

Holliday did not share any details of her eating disorder with the public. According to the National Eating Disorders Association (NEDA), anorexia is characterized by weight loss, generally from restricting calories, or behaviors such as compulsive exercise, binging or purging food or taking laxatives, often motivated by a heightened fear of weight gain, despite low body weight. While another diagnosis, atypical anorexia, meets the criteria of traditional anorexia, except for low body weight. "Atypical anorexia is anorexia, but with weight stigma," Chelsea Kronengold, a spokesperson for NEDA, explains to Yahoo Life.

Atypical anorexia is classified under "Other Specified Feeding or Eating Disorders" (OSFED), what Kronengold calls "a catch-all phrase for disorders that don't fit neatly into a box." Other examples of OSFED: Purging disorder without bulimia, or "night eating," described by NEDA as eating after waking up or eating excessively after dinner.

"With atypical anorexia, the medical and psychological complications mirror traditional anorexia, but due to stigma, it's often misdiagnosed or under-diagnosed," says Kronengold. "Which perpetuates a false narrative that these eating disorders aren't as serious."

There's a false belief that eating disorders are about weight, says Kronengold. "Weight can be a manifestation of the illness but in nature, they are biological, social and psychological illnesses, in which food is used as a coping mechanism, particularly after trauma." And anyone can develop an eating disorder. "It doesn't discriminate based on age, race, socioeconomic status, weight or body shape."

The details of Holliday's health are her business alone, but her admission will undoubtedly help shed stigma. "To everyone that keeps saying 'you're looking healthy lately' or 'You are losing weight, keep it up!' Stop," she wrote Instagram. "Don't. Comment. On. My. Weight. Or. Perceived. Health. Keep. It. To. Yourself. Thanks."

If you or someone you know is struggling with an eating disorder, you can contact NEDA's toll-free, confidential Helpline at www.nationaleatingdisorders.org/helpline.

Read more from Yahoo Life:

• AnnaLynne McCord reveals she has dissociative identity disorder. Experts explain what that means.

• Lana Condor makes self-care a priority amid anti-Asian violence: 'I didn't feel safe'

• Josie Canseco opens up about ‘body dysmorphia’: ‘I can’t remember the last time I looked in the mirror and was happy with how I looked’

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